A = (x+y)^2 + (x-y)y - (2x-y)^2
A = x^2 +2xy +y^2 + xy - y^2 -(4x^2-4xy+y^2)
A = x^2 + 3xy - 4x^2 + 4xy - y^2
A = -3x^2 + 7xy - y^2
B = (2x - 3)^2 - (x - 2)(x - 1)
B = 4x^2 - 12x + 9 - (x^2 - x - 2x + 2)
B = 4x^2 - 12x + 9 - x^2 + x + 2x - 2
B = 3x^2 - 9x + 7
C = (x - 1)^2 + (x + 2)^2
C = x^2 - 2x + 1 + x^2 + 4x + 4
C = 2x^2 + 2x + 5
D = (x - 1)^2 + (x + 2)^2
D = x^2 - 2x + 1 + x^2 + 4x + 4
D = 2x^2 + 2x + 5
E = (3 + 2x)^2 - 2(x + 1)^2
E = 9 + 12x + 4x^2 - 2(x^2 + 2x + 1)
E = 9 + 12x + 4x^2 - 2x^2 - 4x - 2
E = 2x^2 + 8x + 7